Natural or forced catalyst extrudate breakage is an important phenomenon during catalyst manufacture. Here, a twoparameter model for predicting the reduction in the length to diameter ratio of catalyst extrudates due to breakage by impulsive forces as experienced in a laboratory drop test is developed. Part II will show how both parameters can be correlated with the strength of the extrudates and the severity of the drop test. For breakage by impulsive forces, the model reveals that extrudates are reduced in length to diameter ratio according to a pseudosecond-order break law. Also, a tie-in exists with the well-known Golden Ratio that is famous for its inherent esthetic value. Applying the model to cases of "severity sequencing" and "severity conditioning" reveals the nonlinear behavior of the length to diameter ratio and yields results that are often nonintuitive and hard to get without this engineering analysis.

This article describes the reduction of the length to diameter ratio of extrudates, by breakage on collision with a surface. The approach links the rupture force of the extrudate by bending to the impulsive force the extrudate experiences due to collision. The bending or flexural strength of the extrudate is described by the Euler-Bernoulli modulus of rupture. The impulsive force the extrudate experiences is described by Newton's second law. We apply the force balance at the asymptotic length to diameter ratio which is reached after many repeated impacts. This balance yields a dimensionless group as the ratio of the rupture force by bending to the impulsive force by collision. The analysis shows that the asymptotic length to diameter ratio is directly proportional to the square root of this group. This dimensionless group also allows one to define a severity of the collision via the impact velocity and the time of contact of the collision.

A correlation is demonstrated to predict the reduction in the mean length‐to‐diameter ratio of catalyst extrudates by breakage due to stress in a fixed bed. The stress can be caused either by the reactor load or it can be externally applied as in the bulk crush strength measurement. The strength characteristic of particular interest here is the extrudate bending strength characterized by the Euler‐Bernoulli modulus of rupture. The balance of the bending strength to the applied stress leads to a new dimensionless group. Extrudates in a fixed bed start to break above a specific critical stress, and their mean length‐to‐diameter ratio then becomes linearly proportional to this dimensionless group to the power one‐third.

The mechanical strength of extruded catalysts and their natural or forced breakage by either collision against a surface or by a compressive load in a fixed bed are important phenomena in catalyst technology. The mechanical strength of the catalyst is measured here by its bending strength or flexural strength. This technique is relatively new from the perspective of applying it to commercial catalysts of typical sizes used in the industry. Catalyst breakage by collision against a surface is measured after a fall of the extrudates through the ambient air in a vertical pipe. Quantifying the impact force is done theoretically by applying Newton's second law. Measurement of catalyst breakage due to stress in a fixed bed is done following the standard procedure of the bulk crush strength test. Novel here is the focus on measuring the reduction in the length to diameter ratio of the extrudates as a function of the stress.

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